Patients with Diamond-Blackfan anemia 4 years of age and older who weigh at least 27 pounds and who are dependent on red blood cell transfusions may be eligible for this study. Candidates will have a medical history taken and a physical examination and will be seen by the Clinical Center's Department of Medicine Transfusion for leukapheresis evaluation. They will have a bone marrow aspiration and biopsy to confirm the diagnosis of DBA. For these tests, the hip area is anesthetized and a needle is used to draw bone marrow from the hipbone. If needed, the procedure will be done under sedation.